The present invention relates to a pneumatic tire having improved turnability during high speed running. More specifically, the invention relates to a pneumatic tire which is suitably used for racing.
With heightened vehicular performance in recent years, further improvement has been demanded for tire turnability during high speed running. Specifically, an excessive lateral force is applied to an outer side of a turning tire when a vehicle is turned during high speed running. A side section and a bead section outside the vehicle fall to the inner side of the tire. Consequently, limitation is put on turnability.
Conventionally, efforts have been made to improve turnability during high speed running by preventing falling of the bead section during turning. For example, a bead section structure was presented (Japanese Unexamined Patent Laid-Open No. 6 (1994)-227216), which uses a bead core made of single strand steel, a rubber stock having hardness set in a range of 80xc2x0 to 98xc2x0 of JIS-A hardness and arranged in a bead toe section, and a chafer composed of a non-metallic fiber cord and arranged on an outer surface of the rubber stock.
However, the foregoing bead section structure has been unable to satisfy a recent demand for higher speed driving. For example, it is impossible to secure driving stability when a vehicle is run on a comer of a 100 m radius at a high speed of 200 km/h.
An object of the present invention is to provide a pneumatic tire capable of securing high speed turnability, for example, when a vehicle is run on a comer of a 100 m radius at a high speed of 200 km/h or higher.
In order to achieve the foregoing object, the present invention provides a pneumatic tire which comprises carcass layers provided between a pair of bead cores, one in a left bead section and the other in a right bead section and a belt layer arranged outside the carcass layers and around a tire in a tread section. A reinforcing rubber layer made of short fiber reinforced rubber is arranged in an area of the bead section from a bead toe section along a tire inner wall surface.
Also, in order to achieve the object, the present invention provides a pneumatic tire comprising carcass layers provided between a pair of bead cores, one in a left bead section and the other in a right bead section and a belt layer arranged outside the carcass layers and around a tire in a tread section. A reinforcing rubber layer having hardness set in a range of 90xc2x0 to 99xc2x0 of JIS-A hardness is arranged in an area of the bead section from a bead toe section along a tire inner wall surface. Further, a chafer composed of a non-metallic fiber cord is provided to cover an outer side of the reinforcing rubber layer from the tire inner wall surface to a bead seat, the fiber cord having a strength of at least 0.25 kN/cord and an elastic modulus of at least 20 kN/Mm2.
In the pneumatic tire of the present invention, an area of the bead section from the bead toe section to the tire inner wall surface includes (1) a reinforcing rubber layer made of short fiber reinforced rubber, or alternatively (2) a reinforcing rubber layer having hardness set in the range of 90xc2x0 to 99xc2x0 of JIS-A hardness. Further, an outer side of the reinforcing rubber layer is covered with a chafer composed of a non-metallic fiber cord from the tire inner wall surface to the bead seat area, the fiber cord having strength of at least 0.25 kNI/cord and an elastic modulus of at least 20 kN/mm2. Accordingly, even when a vehicle is turned on a corner of a 100 m radius at a high speed of 200 km/h or higher, since the reinforcing rubber layer of the bead toe section exhibits a high compressive strength to suppress large deformation of the tire side section, turnability can be improved.